Stress Corrosion Crack Initiation of Alloy 600 and Alloy 690 in Hydrogenated Supercritical Water.

Stress corrosion crack (SCC) initiation of highly resistant materials can be studied by conducting accelerated testing as long as there is no change in the cracking mechanism. The objective of this dissertation is to determine if accelerated SCC initiation testing of Alloy 600 and Alloy 690 can be conducted without changing the mechanism of crack initiation between subcritical and supercritical water. Unfortunately, the mechanism of crack initiation of these alloys is not known. This makes demonstrating whether there is a change in the SCC mechanism dependent on determining if there is a change in the oxidation, stress corrosion crack initiation morphology, and the temperature dependence of crack initiation between subcritical and supercritical water. The corrosion environment was maintained at a fixed electrochemical potential above the Ni/NiO phase transition in the NiO stable regime by controlling the dissolved hydrogen concentration, with the location of the boundary determined by exposures of pure nickel. Exposures of unstressed corrosion coupons of Alloy 600 and 690 were conducted in hydrogenated subcritical and supercritical water for characterization of the oxide morphology, structure, and composition. Tensile bars of Alloy 600 and Alloy 690 were strained in constant extension rate tensile experiments in both environments to characterize the crack initiation morphology and to determine the temperature dependence of crack initiation. The oxidation for both alloys was consistent between subcritical and supercritical water, composed of a multi-layer oxide structure composed of particles of NiO and NiFe2O4 formed by precipitation on the outer surface and a chromium rich inner oxide layer formed by diffusion of oxygen to the metal-oxide interface. The crack initiation morphology of Alloy 690 was consistent between subcritical and supercritical water, and a mechanism of crack initiation was developed. The SCC initiation temperature dependence of both alloys shows no discontinuity or change in slope in the activation energy at the critical point. All available evidence supports a consistent mechanism of stress corrosion crack initiation in both hydrogenated subcritical and supercritical water for Alloy 600 and Alloy 690.PhDMaterials Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111594/1/tymoss_1.pd

Extremal Problems in Matroid Connectivity

Matroid k-connectivity is typically defined in terms of a connectivity function. We can also say that a matroid is 2-connected if and only if for each pair of elements, there is a circuit containing both elements. Equivalently, a matroid is 2-connected if and only if each pair of elements is in a certain 2-element minor that is 2-connected. Similar results for higher connectivity had not been known. We determine a characterization of 3-connectivity that is based on the containment of small subsets in 3-connected minors from a given list of 3-connected matroids. Bixby’s Lemma is a well-known inductive tool in matroid theory that says that each element in a 3-connected matroid can be deleted or contracted to obtain a matroid that is 3-connected up to minimal 2-separations. We consider the binary matroids for which there is no element whose deletion and contraction are both 3-connected up to minimal 2-separations. In particular, we give a decomposition for such matroids to establish that any matroid of this type can be built from sequential matroids and matroids with many fans using a few natural operations. Wagner defined biconnectivity to translate connectivity in a bicircular matroid to certain connectivity conditions in its underlying graph. We extend a characterization of biconnectivity to higher connectivity. Using these graphic connectivity conditions, we call upon unavoidable minor results for graphs to find unavoidable minors for large 4-connected bicircular matroids

The Danielson Model of Teacher Evaluation: Exploring Teacher Perceptions Concerning Its Value in Shaping and Improving Instructional Practice

Since the publication of A Nation at Risk in 1983, the school reform movement has offered many contrasting ideas and initiatives to make our nation’s schools more effective and globally competitive. Today’s educational leaders are faced with an array of complex demands as they are challenged at the state and federal level to improve teacher practices and learning outcomes within their schools. One of those demands for New Jersey administrators was to implement a teacher evaluation program that improves teaching and learning during the 2013-2014 school year. Mielke and Frontier (2012) believe that meaningful teacher evaluation has the potential to lead to improved instruction and professional growth and that the key to success in teacher evaluation may very well be the perceptions and attitudes of the teachers as they participate in the process The purpose of this research study was to examine teachers’ perception concerning their school’s evaluation practices utilizing the Danielson Framework, specifically if these teachers believe that it is of value in shaping and improving their instructional practices. This qualitative study gathered data from fifteen teachers from one New Jersey high school through semi-structured interviews and observations of the teachers’ conversations with the researcher. The purposely-selected participants are all teachers at the selected high school representing a wide variety of content areas taught as well as a variety in teaching experience. This research is relevant for school leaders contemplating how best to support, design, develop and implement an effective teacher evaluation system. This research can help districts transform teacher evaluation system from merely an exercise in state compliance into an effective tool that can link effective teacher evaluation to improved teacher practices. The researcher believes that the teachers interviewed in this study perceive that if educators are given the opportunity to reflect deeply on their practice through a common framework like what is presented in the Danielson Framework, teachers can identify both their strengths and weaknesses and set attainable goals. Through active involvement in the evaluation process, evidence-based feedback, and professional discussions between teachers and their supervisors, meaningful teacher evaluation practices can help both the school and the teacher determine the focus of each teachers’ professional development based on what is actually occurring or not occurring in the classroom. The vast amounts of money, energy, and dedication currently being expended by Rolling Hills to reform their teacher evaluation system will only ensure the continuous improvement of teaching and learning if teacher learning is part of their evaluation. If a culture of meaningful evaluation, continuous feedback, and differentiated support does not already exist, then school leaders must provide the communication and actions to win over the trust of its teachers so that they all believe that professional growth is one of the schools purposes of evaluation

The Danielson Model of Teacher Evaluation: Exploring Teacher Perceptions Concerning Its Value in Shaping and Improving Instructional Practice

Since the publication of A Nation at Risk in 1983, the school reform movement has offered many contrasting ideas and initiatives to make our nation’s schools more effective and globally competitive. Today’s educational leaders are faced with an array of complex demands as they are challenged at the state and federal level to improve teacher practices and learning outcomes within their schools. One of those demands for New Jersey administrators was to implement a teacher evaluation program that improves teaching and learning during the 2013-2014 school year. Mielke and Frontier (2012) believe that meaningful teacher evaluation has the potential to lead to improved instruction and professional growth and that the key to success in teacher evaluation may very well be the perceptions and attitudes of the teachers as they participate in the process The purpose of this research study was to examine teachers’ perception concerning their school’s evaluation practices utilizing the Danielson Framework, specifically if these teachers believe that it is of value in shaping and improving their instructional practices. This qualitative study gathered data from fifteen teachers from one New Jersey high school through semi-structured interviews and observations of the teachers’ conversations with the researcher. The purposely-selected participants are all teachers at the selected high school representing a wide variety of content areas taught as well as a variety in teaching experience. This research is relevant for school leaders contemplating how best to support, design, develop and implement an effective teacher evaluation system. This research can help districts transform teacher evaluation system from merely an exercise in state compliance into an effective tool that can link effective teacher evaluation to improved teacher practices. The researcher believes that the teachers interviewed in this study perceive that if educators are given the opportunity to reflect deeply on their practice through a common framework like what is presented in the Danielson Framework, teachers can identify both their strengths and weaknesses and set attainable goals. Through active involvement in the evaluation process, evidence-based feedback, and professional discussions between teachers and their supervisors, meaningful teacher evaluation practices can help both the school and the teacher determine the focus of each teachers’ professional development based on what is actually occurring or not occurring in the classroom. The vast amounts of money, energy, and dedication currently being expended by Rolling Hills to reform their teacher evaluation system will only ensure the continuous improvement of teaching and learning if teacher learning is part of their evaluation. If a culture of meaningful evaluation, continuous feedback, and differentiated support does not already exist, then school leaders must provide the communication and actions to win over the trust of its teachers so that they all believe that professional growth is one of the schools purposes of evaluation

Understanding women's feelings about safety and hazards of street drinking in London through interpretative phenomenological analysis

Aims Drinking alcohol in outdoor public places (e.g. streets and parks) and outside of formally organised events is perceived and reported as antisocial behaviour and may be indicative of a problematic relationship with alcohol, and other clinical needs. This paper aims to address a lack of qualitative research on street drinking in the United Kingdom and develop a textured understanding of the lived-experience of how some women engage in street drinking, in the context of one London borough. Method The authors collected semi-structured interviews as part of a larger mixed methods study on street drinking from April to August 2018. A sub-set of interviews (n = 3) with women who were accessing local drug and alcohol services and had a history of street drinking behaviour were selected as a case series for triangulating analysis with a smaller, homogenous sample. These data were analysed using Interpretative Phenomenological Analysis with a reflexive, feminist, social constructionist approach. Results The authors developed and named a superordinate theme, Constellations of Safety and Hazards for Women Drinking in Public and Private. Within this, four themes were defined and illustrated from the data: Drinking outdoors to be away from hazards at home; Women's awareness of geo-temporal factors to moderate risk; Women identifying risks of accepting drinks from strangers; and Threats of untreated trauma within histories of heavy drinking. Definitions and illustrations from participants aid explanations of how the texts add detail or disruption to dominant discourses. Conclusion The case studies illustrating how these women have experienced alcohol misuse and behaviour change provide reflexive accounts of exercising agency in managing embodied and affective states of vulnerability. This was demonstrated by asserting choice around environmental spaces and friendships, even when still in positions deemed as ‘risky’. These three women's decisions around drinking in public, outdoor spaces were shaped by complex interactions of interpersonal, intrapersonal, socio-economic, and cultural structures. Understanding behaviours is improved with data that situates people in contexts where they experience and make sense of their lives

The Effect of US Energy Policy and Farm Program Payments on the Bio-Fuel Sector: A Regime-Switching Approach

Resource /Energy Economics and Policy,

Unavoidable Minors of Large 4-Connected Bicircular Matroids

It is known that any 3-connected matroid that is large enough is certain to contain a minor of a given size belonging to one of a few special classes of matroids. This paper proves a similar unavoidable minor result for large 4-connected bicircular matroids. The main result follows from establishing the list of unavoidable minors of large 4-biconnected graphs, which are the graphs representing the 4-connected bicircular matroids. This paper also gives similar results for internally 4-connected and vertically 4-connected bicircular matroids

A structure-function characterization of the ER membrane protein atlastin

The biogenesis and maintenance of the entire endomembrane system is dependent upon membrane fusion proteins. Mounting evidence indicates that the integral membrane GTPase Atlastin is a membrane fusion protein involved in the homotypic fusion of the endoplasmic reticulum (ER) membrane suggesting a role in the biogenesis and maintenance of ER structure. I helped show that recombinant Drosophila atlastin is able to promote the fusion of synthetic membranes in vitro and that this fusion is dependent upon atlastin GTPase activity. The structure-function experiments presented here assist in elucidating domains required in the mechanism of atlastin mediated membrane fusion. ER homotypic fusion is dependent upon the self-association of Atlastin subunits in adjacent membranes to bring the bilayers into close molecular contact. Atlastin dimerization occurs in the presence of GTPγS but not GDP and stable dimerization is dependent upon a juxtamembrane middle domain three-helix bundle (3HB). The atlastin GTPase domain and 3HB form a potent soluble domain inhibitor of atlastin homotypic fusion, while the GTPase domain alone shows little inhibition. Designed GTPase domain mutations show that GTP binding and atlastin dimerization is insufficient to support fusion without GTP hydrolysis. Additionally, domain analysis of atlastin reveals that the C-terminal cytoplasmic domain of atlastin is absolutely required for membrane fusion, possibly through a protein-lipid interaction of an amphipathic alpha-helix. Genetic lesions in the human Atlastin-1 gene, SPG3A, result in a form of autosomal dominant hereditary spastic paraplegia (HSP). A better understanding of Atlastin function should lend significant insight into normal ER biogenesis and maintenance, as well as the pathology of human disease

Miniature Autonomous Robots for Pipeline Inspection

Aging natural gas pipeline infrastructure is becoming an increasingly large problem in the United States. There are more than 2.4 million miles of pipelines currently in use, all of which require regular maintenance and inspection to ensure safety. It is estimated that 70% of these lines were installed prior to the widespread use of the most common inspection tool, pigs, and therefore require some other tool to carry out tasks such as direct line inspection, pipeline mapping, gas quality monitoring, and cleaning. This has prompted a large growth in the area of robotic inspection devices to fill this market gap. However, many of the robots developed either fall short of true autonomy, are unable to operate in live flow conditions, or are designed for only a specific pipe size. This thesis details the design of a robotic platform called MARPI, or Miniature Autonomous Robot for Pipeline Inspection, which addresses the weaknesses of both pigs and previous robots. MARPI is a wheeled robot that was developed to include several key features: energy harvesting, wireless communication, onboard navigation system, and a small profile and footprint in the pipe. The robot uses two 150:1 micro gear motors for its drive mechanism and features a permanent Neodymium magnet to make the robot adhere to the surface of steel pipes. The energy harvesting system was characterized through a series of wind tunnel experiments which showed that to maximize the power generated it is best to have a turbine with a high number of buckets/blades, streamlined bucket geometry, and a relatively large offset from a bluff body below. To carry out the design of MARPI, a statics model was developed and used to predict the magnetic force required to adhere to and avoid sliding in the pipe, and the motor torque required to propel the robot. This model was used to analyze the performance of the robot as a function of robot size. Key results show that to minimize power consumption, the robot should travel vertically with the flow, and to maximize range per day, a small robot with a large turbine is best